For 40 years, from the mid-1970s, Kerry swatted Dublin aside like an irritating fly in most big games. They also mastered the art of quiet diplomacy. Say a lot but say nothing. A gentle pat on the head and some nice advice to Dublin to keep trying.

But all is changed, changed utterly, a terrible beauty is born. William Butler Yeats was not talking about Dublin, of course, but the truth is that they have become the equivalent monster that Kerry were in the past.

Jim Gavin has been awarded a Master's degree from the Mick O'Dwyer Institute of smothering opponents with kindness. Reporters must be saying to him at this stage that they will use what he said last week and the week before and just change the name of the county involved. Because every opponent is deemed difficult and his own players have applied themselves very well and they will give their next opponent due consideration and respect. No hostages to fortune there.

Kerry need to discover their mojo today because it has been lost for the last few years against Dublin. Ever since that day in 2011 in the All-Ireland final when they had Dublin skewered with ten minutes to go and managed to lose they have not really taken the fight to Dublin. In the last two games especially, last year's final and the first round of the league, Kerry have folded like wet cards and had no stomach for the battle.

Today presents a test of manhood. That may seem a bit dramatic but you cannot win big games without having the balls for it.

Last September Kerry played no football and had no real fight either apart from the few usual suspects. I can't imagine that will happen today. Kerry have steadily improved in this campaign and gave Roscommon a right pasting in the semi-final.

The weather will help their cause too as they have a lot of skilful players like the Gooch and Darran O'Sullivan inside who will be better suited by the dry ball, even if it is not unknown for rain to fall in Kerry.

They will surely play the three big men - Donaghy, Moran and Sheehan - around midfield, and if they can force Stephen Cluxton to kick long they will win a lot of possession. No player has shown more energy or commitment this year than Kieran Donaghy and he will bring a certain combativeness that Kerry have lacked in recent years.

And yet no team has managed to stop Cluxton for a full game and if he has 25 kick-outs Dublin will claim possession on three-quarters of those.

Kerry have a very strong team in the field and I expect they will perform as if this is the last game any of them will ever play but this is Dublin who, unbeaten in 21 competitive games, are becoming the All Blacks of Gaelic football.

They have their system and it does not make that much difference who starts and who comes on. The type of play remains largely the same and close games are made look easy in the last ten minutes. Maybe that is because Dublin have a better team on at the finish of the game.

Dublin have now the most mobile team that has ever galloped around Croke Park and the fast sod suits their play perfectly. Everyone now is a footballer first and positions are more or less irrelevant except for a few defenders. The obvious one here is Cian O'Sullivan, who covers for everybody. It means that the likes of Philly McMahon and Johnny Cooper can attack knowing that the henhouse door is bolted tight. Last September Kerry's flaws seemed to be exposed with Colm Cooper forced to defend on McMahon. That is a bit simplistic. McMahon would go forward even if Messi or Ronaldo were on him so it should have been possible to have someone else covering those runs.

The other part of those marking arrangements was that it allowed McMahon to rough up the Gooch a bit and there was nobody around big enough or brave enough just to let him know the boundaries. Expect that to be a flashpoint today and this match will be a flinty affair as Kerry cannot afford to go down without giving blood in the cause.

Dublin seem able to play football at a different level than any team I have seen, rough or smooth, fast or slow, defence or attack. Nobody has the equivalent in sheer quality of McMahon, Connolly, Flynn, Andrews, Brogan, and about 20 more. Mannion is a huge asset and James McCarthy is the best player in the country. They seem impossible to beat no matter what tactics or team take the field.

This game is much more important to Kerry than Dublin. A win would set the Kingdom up for the year but if they can't beat Dublin now they will have less chance later in the season. So players like Paul Murphy will have to show the sort of form that has made him a very good outlet from defence and a good forward at the same time. More importantly, it must be war for Kerry and see if that works because the nice approach cut no ice recently.

In ancient Greece there was a fearsome group called the Spartans. Inward-looking and self-sufficient, they were feared warriors as they lived an austere life, despising luxury and living in cities with no walls or grand buildings. The Spartan mothers advised their sons before battle to come home with their shields, or on them. Either death or glory. Kerry may not have to go quite that far but there is honour involved as well as football. I expect that honour will be restored.

Another match of great importance takes place earlier and this is going to be a long day in Croke Park with the 1916 show afterwards. Even so I am really looking forward to three great spectacles with Cavan versus Tyrone starting things off.

I have seen both teams in the flesh this year as well as on television. There were no hard luck stories in the second division of this year's Allianz League as the best two teams undoubtedly won promotion. Cavan were getting visibly stronger with every game. They are on the move, a team of the future.

The same applies to Tyrone and it does appear that there is less messing than last year. Their form of defence is not attractive to watch but they are an exciting team with the ball.

They have a fair panel now and the Cavanaghs are still providing the leadership, while I have been very impressed with Rory Brennan, Tiernan McCann, Peter Harte and Mattie Donnelly. They are already better than most teams in the top division and should be favourites for Ulster and have a real chance of winning the All-Ireland.

Cavan are probably a bit behind this and will get better over the next couple of years. It is amazing how they have changed their style of football, from absolutely stink to free-flowing quality, even if defence is still tight. Killian Clarke looks like a proper footballer and so does Gearóid McKiernan and Dara McVeety but Cavan have a panel and there were several times over the last few months where their subs were the key to victory. Tyrone won the earlier league encounter and should do so again but this may only be the beginning for Cavan.